How Interest Really Works (And Why Most People Get It Wrong)

Interest can make you rich or keep you broke — depending on which side you're on. APR vs APY, compounding explained with real examples.

7 min read · Published 2026-03-17 · Updated 2026-04-04

Frequently asked questions

What's the difference between interest rate and APY?

The interest rate is the base percentage. APY (Annual Percentage Yield) includes the compounding effect, so it's always equal to or slightly higher than the stated rate. APY tells you what you actually earn in a year.

How often should interest compound for the best results?

Daily compounding beats monthly, which beats yearly — but the differences are small. Going from annual to monthly compounding matters more than going from monthly to daily. Most savings accounts compound daily, which is ideal.

Can I lose money in a savings account with interest?

Your nominal balance won't decrease (it's FDIC insured). However, if your interest rate is below inflation, your money loses purchasing power over time. A 0.01% account during 3% inflation means you're effectively losing 2.99% per year in real value.

Why do credit cards charge so much more interest than savings accounts pay?

Banks earn profit on the spread between what they charge borrowers and what they pay savers. Credit cards are also unsecured (no collateral), so the risk is higher, which justifies higher rates from the lender's perspective.